There is an apparatus disclosed in Patent Document 1 as a conventional hermetically sealed kneader which kneads a kneading material such as rubber, plastics, or the like. The hermetically sealed kneader of Patent Document 1 is configured so that the kneading material such as rubber, plastics, or the like injected into a kneading chamber is kneaded by two rotors arranged in the kneading chamber and so that the kneading material turned into a desired kneaded state is taken out to the outside. These two rotors are each configured so that both ends of a shaft are rotatably supported by bearings. The end of each rotor at the drive side is an input shaft projected to the outside. An output shaft of a drive unit adjacently arranged and the input shaft are coupled to each other via a coupling device such as a gear coupling.
In the hermetically sealed kneader of Patent Document 1, the kneading material such as rubber, plastics, or the like is inputted with various types of additives from a slot at the upper side into a hopper by a predetermined volume. This kneading material is injected into the sealed kneading chamber by a push-in action of a floating weight. The kneading material injected into the kneading chamber in this manner is kneaded by the rotors rotating in directions different from each other. A driving force (rotation) of a motor is transmitted via a speed reducer to the respective rotors. The respective rotors rotate so as to wipe an inner wall of the kneading chamber and rotate in the different directions from each other. Thus, a resin material (the kneading material) injected into the kneading chamber is kneaded with the various types of additives; thereafter, the kneading material turned into the desired kneaded state is taken out to the outside.
Further, a blade (kneading blade) is arranged on an outer circumferential surface of the rotor. In the hermetically sealed kneader of Patent Document 1, this blade is configured to be twisted in a spiral shape with respect to an axis line of the rotor. The kneading material such as rubber, plastics, or the like is injected in the axial direction by an action of this twisted blade; therefore, a flow to feed the kneading material in the axial direction is generated. Furthermore, the two rotors are configured so that the blades are respectively twisted so as to generate flows in directions different from each other with respect to the axial direction, thereby allowing the kneading material to be fed so that the material is circulated in the chamber. Thus, the kneading material may be effectively kneaded.
In addition, in the hermetically sealed kneader disclosed in Patent Document 1, that is, in a general hermetically sealed kneader, the kneading material is fed in the axial direction by the blade that is formed on the rotor to be twisted in a spiral shape; therefore, its reaction generates a reaction force (thrust load) acting in the axial direction. Such thrust load significantly affects a life span of the bearing that supports the rotor. Therefore, in order to determine the life span of the bearing, it is necessary that a thrust load is accurately measured. Further, in a case where a thrust load cannot be accurately perceived, a problem that a thrust load greater than a designed load is applied to the bearing; on the contrary, a bearing over the specification is utilized, may be caused. Accordingly, in a case where the aforementioned type of bearing is applied, preferably, a means which can accurately measure a load in a thrust direction, acting on the rotor, is provided.
For example, Patent Document 2 discloses a method in which a load sensor is provided between a bearing body and a casing to thereby measure a load which acts on a bearing.